Magnetic disks and disk drives are conventionally employed for storing data in magnetizable form. Preferably, one or more disks are rotated on a central axis in combination with data transducing heads positioned in close proximity to the recording surfaces of the disks and moved generally radially with respect thereto. Magnetic disks are usually housed in a magnetic disk unit in a stationary state with a magnetic head having a specific load elastically in contact with and pressed against the surface of the disk. Data are written onto and read from a rapidly rotating recording disk by means of a magnetic head transducer assembly that flies closely over the surface of the disk. Preferably, each face of each disk will have its own independent head.
In FIG. 1, an embodiment of a disc drive storage device 100 is illustrated. Disc drive 100 includes a disc pack 126 having storage surfaces 106 that are typically layers of magnetic material that are deposited using microstructure fabrication techniques. The disc pack 126 includes a stack of multiple discs and the read/write head assembly 112 includes a read/write transducer or head 110 for each stacked disc. The head 110 is typically formed using microstructure fabrication techniques. Disc pack 126 is spun or rotated as shown by arrow 107 to allow read/write head assembly 112 to access different rotational locations for data on the storage surfaces 106 on the disc pack 126.
Read/write head assembly 112 is actuated to move radially, relative to the disc pack 126, as shown by arrow 122 to access different radial locations for data on the storage surfaces 106 of disc pack 126. Typically, the actuation of read/write head assembly 112 is provided by a voice coil motor 118. Voice coil motor 118 includes a rotor 116 that pivots on axle 120 and an arm 114 that actuates the read/write head assembly 112. Disc drive 100 includes electronic circuitry 130 for controlling the operation of the disc drive 100 and transferring data in and out of the disc drive.
Typically, the disc drive head 110 slides over the storage surface 106 in the disc drive 100 as illustrated. If there are particles of a large enough dimension between the sliding surfaces, then there is an increased risk that one of the sliding surfaces may be damaged during operation. In modern disc drives a critical dimension can approach 5 nanometers between the head 110 and the storage surface 106. Particles can cause damage and need to be removed from the sliding surfaces before assembly of the disc drive 100.
A sectional view of a disk recording medium, which is generally shaped like a disc, is shown in FIG. 2. Even though FIG. 2 shows sequential layers on one side of the non-magnetic substrate 10, it is to sputter deposit sequential layers on both sides of the non-magnetic substrate.
Adverting to FIG. 2, a sub-seed layer 11 is deposited on substrate 10, e.g., a glass or glass-ceramic substrate. Subsequently, a seed layer 12 is deposited on the sub-seed layer 11. Then, an underlayer 13, is sputter deposited on the seed layer 12. An intermediate or flash layer 14 is then sputter deposited on underlayer 13. Magnetic layer 15 is then sputter deposited on the intermediate layer, e.g., CoCrPtTa. A protective covering overcoat 16 is then sputter deposited on the magnetic layer 15. A lubricant topcoat (not shown in FIG. 2 for illustrative convenience) is deposited on the protective covering overcoat 16.
The disk is finely balanced and finished to microscopic tolerances. Take the smoothness of its surface, for example. The drive head rides a cushion of air at microscopic distances above the surface of the disk. So, the surface cannot be too smooth, or the drive lead will end up sticking to the disk, and it cannot be too rough either, or the head will end up getting caught in the microscopic bumps on the surface.
It is considered desirable during reading and recording operations to maintain each transducer head as close to its associated recording surface as possible, i.e., to minimize the flying height of the head. This objective becomes particularly significant as the areal recording density increases. The areal density (Mbits/in2) is the recording density per unit area and is equal to the track density (TPI) in terms of tracks per inch times the linear density (BPI) in terms of bits per inch.
Using chemical and mechanical methods to remove contaminants from the surface of the rigid magnetic medium after the mechanical texture process are proven methods to effectively remove contaminants which degrade the performance of the rigid disk medium. Some larger contaminants in the range of 1-5 microns are easier to remove, but smaller contaminants in the range of 0.1 micron to 1.0 micron are much more difficult to remove.
Contaminants on the surface of the disk can degrade the performance of the rigid magnetic medium. Contaminants that protrude above the flying height of the read/write heads can cause these heads to crash—just like an airplane hitting a small hill. Contaminants that are below the flying height of the read/write heads, but are large enough, will cause a loss of magnetic signal. Some contaminants prevent the succeeding thin film metals (as they are applied through the sputtering process) from adhering completely onto the NiP surface. All these forms of contamination directly lead to magnetic performance failure at the drive.
High area density rigid magnetic medium requires high magnetic track density and high bits per inch. To satisfy these basic magnetic designs, the space between the head and the rigid magnetic medium must be reduced to nanometer level. For example the flying height of 100 Gb/sq-in drive now is around 40 to 50 angstroms. This requires the rigid magnetic medium to have very clean surfaces with very few sub-micron particles and contaminants. This is a very huge challenge because of the very small sizes of the sub-micron particles and contaminants.
In recent years, considerable effort has been expended to achieve high areal recording density. In particular, the requirement to further reduce the flying height of the head imposed by increasingly higher recording density and capacity renders the disk drive particularly vulnerable to head crash due to accidental glide hits of the head and media. To avoid glide hits, a smooth defect-free surface of data zone is desired. The direct result of these demands is tending towards low yield due to less defect tolerance at the surface of the media. Thus, it is desired to arrive at an improved and efficient mechanism for scrubbing/burnishing/polishing the surface of the discs to produce defect-free surface.